From a tract of land, a developer plans to fence a rectangular region and then divide it into two identical rectangular lots by putting a fence down the middle. Suppose that the fence for the outside boundary costs $20 per foot and the fence for the middle costs $8 per foot. If each lot contains 8,640 square feet, find the dimensions of each lot that yield the minimum cost for the fence. length of side parallel to the middle fence length of side perpendicular to the middle fence